Battery charger

ABSTRACT

A charger having a controller with an input and an output, a first terminal for connecting a battery pack to the controller, a connecting line disposed between the first terminal and the input of the controller, a current source connected to the controller for providing power to the battery pack. The current source provides power to the battery pack via the connecting line. The controller sends a pulse signal unto the connecting line via the output, so that the controller can determine whether the battery pack is connected to the charger by the presence of the pulse signal in the input of the controller.

FIELD OF THE INVENTION

This invention relates generally to battery chargers and more particularly to battery chargers with protection circuitry.

BACKGROUND OF THE INVENTION

The battery packs for portable power tools, outdoor tools and certain kitchen and domestic appliances may include rechargeable batteries, such as lithium, nickel cadmium, nickel metal hydride and lead-acid batteries, so that they can be recharged rather than be replaced. Thereby a substantial cost saving is achieved.

It is preferable to provide a charger that recognizes when a battery pack has been connected in order to begin charging.

SUMMARY OF THE INVENTION

In accordance with the present invention, an improved battery pack charger is employed. The charger includes a controller having an input and an output, a first terminal for connecting a battery pack to the controller, a connecting line disposed between the first terminal and the input of the controller, a current source connected to the controller for providing power to the battery pack, the current source providing the power to the battery pack via the connecting line, wherein the controller sends a pulse signal unto the connecting line via the output, whereby the controller determines whether the battery pack is connected to the charger by the presence of the pulse signal in the input of the controller.

Additional features and benefits of the present invention are described, and will be apparent from, the accompanying drawings and the detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate preferred embodiments of the invention according to the practical application of the principles thereof, and in which:

FIG. 1 is a simplified block diagram of a battery pack and charger;

FIG. 2 is a flowchart showing a method according to the present invention;

FIG. 3 is a schematic diagram of the charger according to the present invention.

DETAILED DESCRIPTION

The invention is now described with reference to the accompanying figures, wherein like numerals designate like parts.

Referring to FIGS. 1-2, a battery pack 10 is connected to a charger 20. Battery pack 10 may comprise a plurality of battery cells 11 connected in series and/or parallel, which dictate the voltage and storage capacity for battery pack 10. Battery pack 10 may include three battery contacts: first battery contact 12, second battery contact 13, and third battery contact 14. Battery contact 12 is the B+ (positive) terminal for battery pack 10. Battery contact 14 is the B− or negative/common terminal. Battery contact 13 is the S or sensing terminal. Battery contacts 12 and 14 receive the charging current sent from the charger 20 (preferably from current source 22, as discussed below) for charging the battery pack 10.

As shown in FIG. 1, the battery cells 11 are connected between the battery contacts 12 and 14. In addition, preferably connected between battery contacts 13 and 14 is a temperature sensing device 15, such as a negative temperature co-efficient (NTC) resistor, or thermistor, R_(T). The temperature sensing device is preferably in closer proximity to the cells 11 for monitoring of the battery temperature. Persons skilled in the art will recognize that other components, such as capacitors, etc., or circuits can be used to provide a signal representative of the battery temperature.

The charger 20 preferably comprises a controller 21, which in turn includes positive terminal (B+) 17 and negative (B−) terminal 18, which are coupled to battery pack 10 via battery contacts 12 and 14, respectively. The positive terminal may also act as an input, preferably an analog/digital input A/D, in order for the controller 21 to detect the battery pack voltage. In addition, the controller 21 may include another input TC, preferably an analog/digital input, which is coupled to the temperature sensing device 15 via the third battery contact 13 (S). This allows the controller 21 to monitor the battery temperature.

Controller 21 may include a microprocessor 23 for controlling the charging and monitoring operations. Controller 21 may control a charging power source for providing power to the battery pack 10, such as current source 22 that provides current to battery pack 10. This current may be a fast charging current and/or an equalization current. Current source 22 may be integrated within controller 21.

Controller 21 may have a memory 25 for storing data. Memory 25 may be integrated within controller 21 and/or microprocessor 23.

Controller 21 preferably has a pulse output PO, which sends a pulse signal unto the same line that sends power to the battery pack 10. The pulse signal may have an amplitude of 5 volts. Preferably the pulse signal generated by the controller 21 goes through a diode D23 and/or a resistor R54.

With such arrangement, controller 21 can determine whether a battery pack 10 has been connected to the charger 20. FIG. 2 is a flowchart illustrating the process for determining whether a battery pack 10 has been connected to the charger 20.

First, the current source 22 must be off (ST1). The controller 21 then sends a pulse signal via pulse output PO (ST2).

The controller 21 then checks whether the input A/D has received a pulse (ST3). If a pulse was received, a battery pack 10 is not connected to the charger 20.

On the other hand, if a pulse was not received, the controller 21 would interpret this to mean that a battery pack 10 is connected to the charger 20. Persons skilled in the art will recognize that the voltage at input A/D will be substantially constant since resistor R54 and diode D23 will not allow a significant current to generate an AC signal across the battery. Since the pulse was not received, controller 21 would then start charging battery pack 10 by turning on current source 22 (ST4).

Controller 21 then senses the battery voltage V0 via input A/D (ST5). Controller 21 compares battery voltage V0 to a certain threshold X (ST6). If battery voltage V0 is below threshold X, charging continues and controller 21 continues to sense and compare the battery voltage V0.

If battery voltage V0 exceeds (or is equal to) threshold X, controller 21 then assumes that the battery pack 10 has been removed from charger 20 and stops charging by turning the current source off. Persons skilled in the art will recognize that it is preferable to provide a relatively high threshold so as to not prematurely terminate charging, resulting in an undercharged battery pack. Accordingly, it is preferable to provide a threshold of at least 30 volts.

FIG. 3 is an exemplary schematic diagram of the charger of FIG. 1. Preferably, the values of the different components of are as follows: C1 0.1 microfarads C2A 1,000 microfarads C2B 1,000 microfarads C2C 1,000 microfarads C3 0.1 microfarads C5 102 picofarads C6 0.1 microfarads C7 47 microfarads C8 0.001 microfarads C9 0.1 microfarads C10 0.001 microfarads C11 220 picofarads C12 0.1 microfarads C14 0.01 microfarads C15 0.1 microfarads C22 1 microfarads C26 1 microfarads C29 0.1 microfarads C51 0.1 microfarads C52 0.01 microfarads C62 100 picofarads C65 0.001 microfarads C67 0.01 microfarads C68 0.1 microfarads C69 47 microfarads C70 0.0022 microfarads C71 0.22 microfarads C72 0.1 microfarads CR51 Diode FRD T220 STPR1020CT D2 Diode FRD 1 A 1000 V DO204 BYV26E D6 Diode SW .3 A 75 V MELF D7 Diode SW 200 mA 75 V DO-35 D8 Diode SW .3 A 75 V MELF D9 Diode SW 200 mA 75 V DO-35 D10 Diode SW .3 A 75 V MELF D11 Diode SW .3 A 75 V MELF D17 Diode SW .3 A 75 V MELF D21 Diode SW .3 A 75 V MELF D22 Diode SW .3 A 75 V MELF D23 Diode SW 200 mA 75 V DO-35 D29 Diode SW .3 A 75 V MELF FL1 LF 780 microhenries IC1 UC3845BN IC2 Microprocessor IC4 LM358 L1 1.1 microhenries L2 1.1 microhenries NTC1 thermistor, 100K Q1 FET 60 V 50 A T220 IRFZ44N Q2 FET 60 V 50 A T220 IRFZ44N Q3 MMBT4401 SMT Q7 MMBT4403 SMT Q8 MMBT4401 SMT Q9 MMBT4401 SMT R2 47 kiloohms R4 5.1 kiloohms R5 3 kiloohms R6 1 kiloohms R7 33 ohms R8 33 ohms R9 1 kiloohms R10 43 kiloohms R11 12 kiloohms R12 220 kiloohms R13 100 ohms R14 18 kiloohms R15 2.2 ohms R16 220 kiloohms R27 80.6 kiloohms R28 14 kiloohms R31 47.5 kiloohms R33 39 kiloohms R43 470 ohms R47 8.25 kiloohms R48 8.2 kiloohms R49 10 kiloohms R52 1 kiloohms R53 4.02 kiloohms R54 470 ohms R55 4.7 kiloohms R56 82 kiloohms R57 2 kiloohms R58 1 kiloohms R59 10 kiloohms R60 82 kiloohms R61 100 kiloohms R62 100 kiloohms R63 100 kiloohms R64 470 ohms R66 10 kiloohms R67 100 kiloohms R68 1 kiloohms R69 10 kiloohms R76 100 kiloohms R83 100 kiloohms R86 910 ohms R87 1 kiloohms R94 330 ohms R95 1.2 kiloohms R96 1.5 kiloohms R97 1.2 kiloohms R98 30 kiloohms R99 200 kiloohms R100 10 kiloohms R101 10 kiloohms R102 300 ohms R103 10 kiloohms T1 Transformer U4 Voltage Regulator IC 5 V 0.1 A T92 3PIN 7805 VR51 Variable Resistor 1 kiloohms Z1 Varistor 20 VAC 6 J 1000 A ZD1 Zener Diode 0.5 W 18 B MELF ZD2 Zener Diode 0.5 W 20 B MELF ZD3 Zener Diode 0.5 W 6.2 B MELF ZD4 Zener Diode P6KE51A ZD5 Zener Diode 0.5 W 15 B MELF ZD6 Zener Diode 0.5 W 15 B DO-35 ZD7 Zener Diode 0.5 W 5.1 C MELF ZD8 Zener Diode 0.5 W 5.1 C MELF ZD9 Zener Diode 0.5 W 12 C MELF ZD51 Zener Diode 0.5 W 36 V RLZTE1139B/TZMB36 MELF

Persons skilled in the art will recognize that the pulse output PO and input are pins 15 and 7 of IC2, respectively. Persons skilled in the art will also recognize that diode D23 and resistor R54 are the same components in FIGS. 1 and 3.

Persons skilled in the art should recognize that the charger shown in FIG. 3 is connectable to a vehicle battery, rather than to an AC source. Nevertheless, persons skilled in the art will know how to modify the power supply within the charger to accept power from an AC source.

Finally, persons skilled in the art may recognize other additions or alternatives to the means disclosed herein. However, all these additions and/or alterations are considered to be equivalents of the present invention. 

1. A charger comprising: a controller having an input and an output; a first terminal for connecting a battery pack to the controller; a connecting line disposed between the first terminal and the input of the controller; a current source connected to the controller for providing power to the battery pack, the current source providing the power to the battery pack via the connecting line; wherein the controller sends a pulse signal unto the connecting line via the output, whereby the controller determines whether the battery pack is connected to the charger by the presence of the pulse signal in the input of the controller.
 2. The charger of claim 1, wherein the charger is connectable to a vehicle battery.
 3. The charger of claim 1, wherein the charger is connectable to an AC source.
 4. A charger/battery pack combination comprising: a battery pack; a charger for charging the battery pack comprising: a controller having an input and an output; a first terminal for connecting the battery pack to the controller; a connecting line disposed between the first terminal and the input of the controller; a current source connected to the controller for providing power to the battery pack, the current source providing the power to the battery pack via the connecting line; wherein the controller sends a pulse signal unto the connecting line via the output, whereby the controller determines whether the battery pack is connected to the charger by the presence of the pulse signal in the input of the controller.
 5. The charger/battery pack combination of claim 4, wherein the charger is connectable to a vehicle battery.
 6. The charger/battery pack combination of claim 4, wherein the charger is connectable to an AC source.
 7. A method for detecting whether a battery pack is connected to a charger, the method comprising: providing the charger a controller having an input and an output, a first terminal for connecting the battery pack to the controller, a connecting line disposed between the first terminal and the input of the controller, a current source connected to the controller for providing power to the battery pack, the current source providing the power to the battery pack via the connecting line; sending a pulse signal unto the connecting line via the output; and detecting a presence of the pulse signal in the input of the controller.
 8. The method of claim 7, further comprising turning off the current source prior to sending the pulse signal.
 9. The method of claim 7, further comprising turning on the current source if the pulse signal is not detected.
 10. The method of claim 7, further comprising sensing a voltage of the battery pack.
 11. The method of claim 10, further comprising comparing the voltage to a predetermined threshold.
 12. The method of claim 11, further comprising stopping a charging process if the voltage exceeds the predetermined threshold.
 13. The method of claim 11, further comprising continuing a charging process if the voltage is below the predetermined threshold.
 14. The method of claim 11, wherein the predetermined threshold is at least 30 volts. 